Importing a wildcard certificate - reports as invalid

Hello.

I have a GoDaddy wildcard certificate that we have for many purposes. I am now trying to use this with Exchange 2013. I have it in .pfx format and the private key is included.

I can import the certificate without error using PowerShell;
Import-ExchangeCertificate -FileData ([Byte[]]$(Get-Content -Path "C:\Certificates\cert.pfx" -Encoding byte -ReadCount 0)) -Password:(Get-Credential).password

The server has internet access.

Once imported ECP showed "The certificate status could not be determined because the revocation checked failed". I ran "netsh winhttp import proxy ie" and now the certificate reports as Invalid.

Here is a cut down output from Get-ExchangeCertificate | fl
RootCAType     : Unknown
Status             : Invalid
Subject           : CN=*.cert.com, OU=Domain Control Validated, O=*.cert.com 

I have downloaded and imported the intermediate certificates to Local Computer | Intermediate Certificate Authorites

I have also downloaded the root certificate to Trusted Root Certification Authorities although they were already present.

Any ideas as this has got me stumped!